In wireless communication systems, multiple input multiple output (MIMO), is an antenna technique configured to improve the spectral efficiency and thereby boost overall system capacity. The MIMO technique uses a commonly known notation (M×N) to represent MIMO configuration in terms number of transmit (M) and receive antennas (N) on one end of the transmission system. MIMO systems can significantly increase the data carrying capacity of wireless systems. MIMO can be used for achieving diversity gain, spatial multiplexing gain and beamforming gain.
In new radio, sometimes referred to as 5G, user equipment computes channel estimates based on pilot or reference signals from the 5G system, and computes the parameters needed for channel state information (CSI) reporting. A CSI report, including channel quality indicator (CQI) data, is sent from the user equipment to a network device on demand via a feedback channel on request from the network, and/or the user equipment may be configured to send the CSI report periodically. A network scheduler uses this information in choosing the parameters for scheduling of this particular user equipment. The network sends the scheduling parameters to the user equipment in a downlink control channel. After that, actual data transfer takes place from the network to the user equipment.
In new radio, for channel quality indicator (CQI) modulation schemes, the network can configure a user equipment to use a CQI table having a up to a 64 quadrature amplitude modulation (QAM) scheme or to use a CQI table having a up to a 256 QAM modulation scheme. For modulation and coding scheme (MCS) interpretation, the network somewhat similarly configures the user equipment to use a modulation and code rate table for the physical downlink shared channel (PDSCH) with a maximum modulation order of 64 QAM, or to use a different table with a maximum modulation order of 256 QAM. However, the CQI table configuration is indicated when the network configures the CSI reporting configuration, whereas the MCS table is configured when the user equipment is configured for PDSCH transmission in the connected state. As a result, there is a possibility of a mismatch between the configuration of the CQI table and the configuration of the MCS table. For example, if the user equipment is configured with 256-QAM table for CQI, while the MCS table is 64-QAM, the network can never schedule the user equipment with 256-QAM modulation, as the network cannot indicate the 256-QAM modulation. This implies that even though the user equipment is capable of receiving 256 QAM modulation and coding scheme, the network cannot schedule an MCS index with 256 QAM entries. This incurs loss in link throughput and system throughput for 5G systems.